Dioscorea opposita Thunb, commonly known as “yam” that has a long dietary therapy history for diabetes, is widely consumed as a botanical dietary supplement and widely cultivated in China. In this work, a method for rapid screening of α-glucosidase inhibitors from Dioscorea opposita Thunb peel extract was developed using α-glucosidase functionalized magnetic nanoparticles (αG-MNPs) as a solid phase extraction absorbent in combination with high performance liquid chromatography-mass spectrometry (HPLC-MS). Two α-glucosidase inhibitors were selectively extracted and identified as batatasin I and 2,4-dimethoxy-6,7-dihydroxyphenanthrene. Their α-glucosidase inhibitory activities (IC50 = 2.55 mM and 0.40 mM, respectively) were significantly higher than that of acarbose (as control). Taking advantage of the specificity in enzyme binding and the convenience of magnetic separation, this method has great potential for rapid and fast screening of α-glucosidase inhibitors from complex natural resources.

Applying voltammetric, spectroscopic, and molecular docking technology, the binding properties of batatasin derivatives with HSA were systematically estimated. Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) results showed that the common irreversible oxidation peaks of these compounds at 0.50–0.60 V were an adsorption process with equal numbers of electrons and protons. These compounds could interact with HSA and form non-electroactive complexes, at a binding ratio of 1:1. Comparing their association constants with HSA, 2-hydroxy-3,5-dimethoxy-bibenzyl was the strongest, following by demethyl batatasin IV, 2,3-dihydroxy-bibenzyl and 2-(1-phenethyl)phenol which were basically comparable. The equal fluorescent emission point proved further that these compounds interacted with HSA indeed and new complexes generated. The compounds caused a large reduction of α-helix structure in HSA and extension of its peptide chain which were proved by UV-Vis and CD spectrometric results. Molecular docking results directly demonstrated that the compounds bound near Trp-214 in subdomain IIA mainly through hydrogen bonds.

•Spectroscopic and molecular modeling methods were used.•The quenching of DNA–EB system by 5-HMF was a static quenching.•The binding of 5-HMF to DNA was a non- intercalative binding.•Hydrophobic force and hydrogen bonds both played a major role.In this work, the interaction of 5-Hydroxymethyl-2-furfural (5-HMF) with calf thymus DNA (ctDNA) under simulated physiological conditions (Tris–HCl buffer of pH 7.40), was explored by UV absorption spectroscopy, fluorescence spectroscopy and molecular modeling method, using ethidium bromide (EB) as a fluorescence probe of DNA. The fluorescence quenching mechanism of EB–ctDNA by 5-HMF was confirmed to be a static quenching, which derived from the formation of a new complex. The binding constants of 5-HMF with DNA in the presence of EB were calculated to be 2.17 × 103, 4.24 × 103 and 6.95 × 103 L mol−1 at 300, 305 and 310 K, respectively. The calculated thermodynamic parameters, enthalpy change ΔH and entropy change ΔS, suggested that both hydrophobic interactions and hydrogen bonds played a predominant role in the binding of 5-HMF to DNA. According to the UV absorption spectroscopy and melting temperature (Tm) curve results, the binding mode of 5-HMF with DNA was indicative of a non-intercalative binding, which was supposed to be a groove binding. The molecular modeling results showed that 5-HMF could bind into the hydrophobic region of ctDNA and supported the conclusions obtained from the above experiments.Graphical abstract

The interaction between Daphnin with human serum albumin has been studied for the first time by spectroscopic methods including fluorescence quenching technology, circular dichroism (CD) spectroscopy and Fourier transform infrared (FT-IR) spectroscopy under simulative physiological conditions. The results of fluorescence titration revealed that Daphnin can quench the intrinsic fluorescence of HSA by static quenching and there is a single class of binding site on HSA. In addition, the studies of CD spectroscopy and FT-IR spectroscopy showed that the protein secondary structure changed with increases of α-helices at the drug to protein molar ratio of 2. Furthermore, the thermodynamic functions ΔH0 and ΔS0 for the reaction were calculated to be 11.626 kJ mol−1 and 118.843 J mol−1 K−1 according to Van’t Hoff equation. The thermodynamic parameters (ΔH0 and ΔS0) and the molecular modeling study indicated that hydrophobic force played an important role to stabilize the Daphnin–HSA complex, and Daphnin could bind within the subdomain IIA of the HSA.Graphical abstractHighlights► The interaction of HSA and Daphnin was studied by spectroscopic methods. ► The fluorescence quenching mechanism is static quenching. ► The interaction is driven mainly by hydrophobic force. ► The binding constants and thermodynamic parameters were calculated. ► The binding of Daphnin to HSA induced changes in the secondary structure of HSA.